Handling changes in a distributed network management system that uses a logical multi-dimensional label-based policy model

ABSTRACT

A change to a state of a particular managed server within an administrative domain is processed. The administrative domain includes a plurality of managed servers that use management instructions to configure management modules so that the configured management modules implement an administrative domain-wide management policy that comprises a set of one or more rules. A first description of the particular managed server is modified to indicate the particular managed server&#39;s changed state, thereby specifying a second description of the particular managed server. The unmodified first description is compared to the second description, thereby specifying a description change. A determination is made, based on the description change, regarding whether to update management instructions previously sent to the particular managed server.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/810,480, filed Apr. 10, 2013, which is incorporated by referenceherein in its entirety. This application also claims the benefit of U.S.Provisional Application No. 61/899,468, filed Nov. 4, 2013, which isincorporated by reference herein in its entirety. This application isrelated to U.S. application No. TBD (Attorney Docket Number30025-25165), filed on the same day as the present application, which isincorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The subject matter described herein generally relates to the field ofmanaging servers (physical or virtual) of an administrative domain and,in particular, to managing servers according to an administrativedomain-wide policy that adheres to a logical multi-dimensionallabel-based policy model.

2. Background Information

Servers (physical or virtual) of an administrative domain are managedaccording to a policy. For example, a security policy might specifyaccess control and/or secure connectivity, while a resource-usage policymight specify usage of the administrative domain's computing resources(e.g., disks and/or peripherals). Conventional policies referencephysical devices and are expressed in terms of low-level constructs suchas Internet Protocol (IP) addresses, IP address ranges, subnetworks, andnetwork interfaces. These low-level constructs make it difficult towrite a fine-grained policy in an abstract and natural way.

SUMMARY

The above and other issues are addressed by a method, non-transitorycomputer-readable storage medium, and system for processing a change toa state of a particular managed server within an administrative domain.The administrative domain includes a plurality of managed servers thatuse management instructions to configure management modules so that theconfigured management modules implement an administrative domain-widemanagement policy that comprises a set of one or more rules. Anembodiment of the method comprises modifying a first description of theparticular managed server to indicate the particular managed server'schanged state, thereby specifying a second description of the particularmanaged server. The method further comprises comparing the unmodifiedfirst description to the second description, thereby specifying adescription change. The method further comprises determining, based onthe description change, whether to update management instructionspreviously sent to the particular managed server. The method furthercomprises, responsive to determining to update the particular managedserver's management instructions: determining, based on the seconddescription, which rules within the set of rules are currently relevantto the particular managed server, thereby specifying currently-relevantrules; determining whether the currently-relevant rules differ frompreviously-relevant rules, wherein the previously-relevant rules weredetermined based on the unmodified first description; and responsive todetermining that the currently-relevant rules are identical to thepreviously-relevant rules, taking no further action.

An embodiment of the medium stores computer program modules executableto perform steps. The steps comprise modifying a first description ofthe particular managed server to indicate the particular managedserver's changed state, thereby specifying a second description of theparticular managed server. The steps further comprise comparing theunmodified first description to the second description, therebyspecifying a description change. The steps further comprise determining,based on the description change, whether to update managementinstructions previously sent to the particular managed server. The stepsfurther comprise, responsive to determining to update the particularmanaged server's management instructions: determining, based on thesecond description, which rules within the set of rules are currentlyrelevant to the particular managed server, thereby specifyingcurrently-relevant rules; determining whether the currently-relevantrules differ from previously-relevant rules, wherein thepreviously-relevant rules were determined based on the unmodified firstdescription; and responsive to determining that the currently-relevantrules are identical to the previously-relevant rules, taking no furtheraction.

An embodiment of the system comprises a non-transitory computer-readablestorage medium storing computer program modules executable to performsteps. The steps comprise modifying a first description of theparticular managed server to indicate the particular managed server'schanged state, thereby specifying a second description of the particularmanaged server. The steps further comprise comparing the unmodifiedfirst description to the second description, thereby specifying adescription change. The steps further comprise determining, based on thedescription change, whether to update management instructions previouslysent to the particular managed server. The steps further comprise,responsive to determining to update the particular managed server'smanagement instructions: determining, based on the second description,which rules within the set of rules are currently relevant to theparticular managed server, thereby specifying currently-relevant rules;determining whether the currently-relevant rules differ frompreviously-relevant rules, wherein the previously-relevant rules weredetermined based on the unmodified first description; and responsive todetermining that the currently-relevant rules are identical to thepreviously-relevant rules, taking no further action.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a high-level block diagram illustrating an environment formanaging servers (physical or virtual) of an administrative domain,according to one embodiment.

FIG. 2 is a high-level block diagram illustrating an example of acomputer for use as one or more of the entities illustrated in FIG. 1,according to one embodiment.

FIG. 3 is a high-level block diagram illustrating a detailed view of aglobal manager, according to one embodiment.

FIG. 4 is a high-level block diagram illustrating a detailed view of apolicy implementation module of a managed server, according to oneembodiment.

FIG. 5 is a flowchart illustrating a method of generating managementinstructions for a particular managed server, according to oneembodiment.

FIG. 6 is a flowchart illustrating a method of generating aconfiguration for a management module of a managed server, according toone embodiment.

FIG. 7 is a flowchart illustrating a method of monitoring local state ofa managed server and sending local state information to a globalmanager, according to one embodiment.

FIG. 8 is a flowchart illustrating a method of processing a change tothe state of an administrative domain's computer network infrastructure,according to one embodiment.

DETAILED DESCRIPTION

The Figures (FIGS.) and the following description describe certainembodiments by way of illustration only. One skilled in the art willreadily recognize from the following description that alternativeembodiments of the structures and methods illustrated herein may beemployed without departing from the principles described herein.Reference will now be made to several embodiments, examples of which areillustrated in the accompanying figures. It is noted that whereverpracticable similar or like reference numbers may be used in the figuresand may indicate similar or like functionality.

FIG. 1 is a high-level block diagram illustrating an environment 100 formanaging servers (physical or virtual) 130 of an administrative domain150, according to one embodiment. The administrative domain 150 cancorrespond to an enterprise such as, for example, a service provider, acorporation, a university, or a government agency. The environment 100may be maintained by the enterprise itself or by a third party (e.g., asecond enterprise) that helps the enterprise manage its servers 130. Asshown, the environment 100 includes a network 110, a global manager 120,multiple managed servers 130, and multiple unmanaged devices 140. Themultiple managed servers 130 and the multiple unmanaged devices 140 areassociated with the administrative domain 150. For example, they areoperated by the enterprise or by a third party (e.g., a public cloudservice provider) on behalf of the enterprise. While one global manager120, two managed servers 130, and two unmanaged devices 140 are shown inthe embodiment depicted in FIG. 1 for clarity, other embodiments canhave different numbers of global managers 120, managed servers 130,and/or unmanaged devices 140.

The network 110 represents the communication pathway between the globalmanager 120, the managed servers 130, and the unmanaged devices 140. Inone embodiment, the network 110 uses standard communicationstechnologies and/or protocols and can include the Internet. In anotherembodiment, the entities on the network 110 can use custom and/ordedicated data communications technologies.

A managed server 130 is a machine (physical or virtual) that implementsan administrative domain-wide management policy 330 (shown in FIG. 3).In one embodiment, a server is a user-space instance of a virtual server(sometimes referred to as a container, virtualization engine, virtualprivate server, or jail) according to operating system-levelvirtualization, which is a server virtualization method where the kernelof an operating system enables multiple isolated user-space instances,instead of only one instance. If a managed server 130 is a physicalmachine, then the managed server 130 is a computer or set of computers.If a managed server 130 is a virtual machine, then the managed server130 executes on a computer or set of computers. The administrativedomain-wide management policy 330 specifies whether and/or how entitiesassociated with the administrative domain 150 are allowed to access (orbe accessed by) other entities or otherwise consume (or provide)services. For example, the administrative domain-wide management policy330 specifies security or resource usage. A security policy mightspecify access control, secure connectivity, disk encryption, and/orcontrol of executable processes, while a resource-usage policy mightspecify usage of the administrative domain's computing resources (e.g.,disks, peripherals, and/or bandwidth).

A managed server 130 includes a management module 132, a managementmodule configuration 134, and a policy implementation module 136. Themanagement module 132 implements the administrative domain-widemanagement policy 330. For example, in the case of security, themanagement module 132 can be a low-level network or security engine suchas an operating system-level firewall, an Internet Protocol security(IPsec) engine, or a network traffic filtering engine (e.g., based onthe Windows Filtering Platform (WFP) development platform). In the caseof resource usage, the management module 132 can be a disk-usage engineor a peripheral-usage engine.

The management module configuration 134 affects the operation of themanagement module 132. For example, in the case of security, themanagement module configuration 134 can be access control rules appliedby a firewall, secure connectivity policies applied by an IPsec engine(e.g., embodied as iptables entries and ipset entries in the Linuxoperating system), or filtering rules applied by a filtering engine. Inthe case of resource usage, the management module configuration 134 canbe disk-usage policies applied by a disk-usage engine orperipheral-usage policies applied by a peripheral-usage engine.

The policy implementation module 136 generates the management moduleconfiguration 134 based on a) management instructions received from theglobal manager 120 and b) the state of the managed server 130. Themanagement instructions are generated based, in part, on theadministrative domain-wide management policy 330. The management moduleconfiguration 134 generated by the policy implementation module 136implements that administrative domain-wide management policy 330 (to theextent that the policy concerns the managed server 130). This two-stepprocess (generating management instructions and generating themanagement module configuration 134) is referred to as “instantiating” amanagement policy. The policy implementation module 136 also monitorsthe local state of the managed server 130 and sends local stateinformation to the global manager 120.

In one embodiment, the policy implementation module 136 is part of alarger proprietary module (not shown). The proprietary module is loadedonto a device that already has a management module 132 and a managementmodule configuration 134, thereby transforming the device from anunmanaged device 140 to a managed server 130. The policy implementationmodule 136 is further described below with reference to FIGS. 4, 6, and7.

An unmanaged device 140 is a computer (or set of computers) that doesnot include a policy implementation module 136. An unmanaged device 140does not implement the administrative domain-wide management policy 330.However, interaction between a managed server 130 and an unmanageddevice 140 can be subject to the administrative domain-wide managementpolicy 330 (as implemented by the managed server 130). One example of anunmanaged device 140 is a network circuit that is used by anadministrative domain 150. Another example of an unmanaged device 140 isa device used by a person to authenticate himself to the administrativedomain 150 (e.g., a notebook or desktop computer, a tablet computer, ora mobile phone).

The global manager 120 is a computer (or set of computers) thatgenerates management instructions for managed servers 130 and sends thegenerated management instructions to the servers. The managementinstructions are generated based on a) the state of the administrativedomain's computer network infrastructure 320 and b) an administrativedomain-wide management policy 330. The state of the administrativedomain's computer network infrastructure 320 includes descriptions ofmanaged servers 130 and (optionally) descriptions of unmanaged devices140. The global manager 120 also processes local state informationreceived from managed servers 130.

The administrative domain-wide management policy 330 is based on alogical management model that does not reference managed servers 130using low-level constructs such as IP addresses, IP address ranges,subnetworks, and network interfaces. Instead, the logical managementmodel references managed servers 130 based on their high-levelcharacteristics, referred to herein as “labels.” A label is a pair thatincludes a “dimension” (a high-level characteristic) and a “value” (thevalue of that high-level characteristic). A management policyconstructed in this multi-dimensional space is more expressive than amanagement policy constructed according to a single-characteristicnetwork/IP address-based policy model. In particular, expressingmanagement policy using the higher-level abstractions of “labels”enables people to better understand, visualize, and modify managementpolicy.

The logical management model (e.g., the number and types of dimensionsavailable and those dimensions' possible values) is configurable. In oneembodiment, the logical management model includes the followingdimensions and values, as shown in Table 1:

TABLE 1 Example of logical management model Dimension Meaning (M),Values (V) Role M: The role of the managed server within theadministrative domain. V: web, API, database Environment M: Thelifecycle stage of the managed server. V: production, staging,development Application M: The logical application (higher-levelgrouping of managed servers) to which the managed server belongs. V:trading, human resources Line of Business M: The business unit to whichthe managed server belongs. V: marketing, engineering Location M: Thelocation of the managed server. Can be physical (e.g., country orgeographical region) or logical (e.g., network). Physical isparticularly useful for expressing geographic compliance requirements.V: US or EU (physical), us-west-1 or us-east-2 (logical)

The logical management model enables multiple managed servers 130 to begrouped together by specifying one or more labels (referred to herein asa “label set”) that describe all of the managed servers 130 in thegroup. A label set includes either zero values or one value for adimension in the logical management model. A label set need not includelabels for all dimensions in the logical management model. In this way,the logical management model enables the segmentation and separation ofan administrative domain's managed servers 130 and the creation ofarbitrary groupings of managed servers 130. The logical management modelalso allows for a single managed server 130 to exist in multipleoverlapping sets (i.e., multiple overlapping groups of managed servers).The logical management model does not limit the single managed server130 to existing in a hierarchy of nested sets.

For example, in the case of security, segmentation can be used withaccess control policies to define groups of managed servers 130 that aresubject to particular policies. Similarly, segmentation can be used withsecure connectivity policies to define groups of managed servers 130 andthe policies that apply to intra-group communications and inter-groupcommunications. So, communications among a first group of managedservers 130 (specified by a first label set) can be restricted to afirst secure connection setting (e.g., secure connection not required),and communications between the first group of managed servers and asecond group of managed servers (specified by a second label set) can berestricted to a second secure connection setting (e.g., IPsecEncapsulating Security Payload (ESP)/Authentication Header (AH) AdvancedEncryption Standard (AES)/Secure Hash Algorithm-2 (SHA-2)).

Each managed server 130 in the environment 100 implements theadministrative domain-wide management policy 330 (to the extent that thepolicy concerns the managed server 130). As a result, the administrativedomain-wide management policy 330 is applied in a distributed fashionthroughout the administrative domain 150, and there are no choke points.Also, the administrative domain-wide management policy 330 is applied atthe logical level independent of the administrative domain's physicalnetwork topology and network addressing schemes.

The global manager 120, the state of the administrative domain'scomputer network infrastructure 320, and the administrative domain-widemanagement policy 330 are further described below with reference toFIGS. 3, 5, and 8.

FIG. 2 is a high-level block diagram illustrating an example of acomputer 200 for use as one or more of the entities illustrated in FIG.1, according to one embodiment. Illustrated are at least one processor202 coupled to a chipset 204. The chipset 204 includes a memorycontroller hub 220 and an input/output (I/O) controller hub 222. Amemory 206 and a graphics adapter 212 are coupled to the memorycontroller hub 220, and a display device 218 is coupled to the graphicsadapter 212. A storage device 208, keyboard 210, pointing device 214,and network adapter 216 are coupled to the I/O controller hub 222. Otherembodiments of the computer 200 have different architectures. Forexample, the memory 206 is directly coupled to the processor 202 in someembodiments.

The storage device 208 includes one or more non-transitorycomputer-readable storage media such as a hard drive, compact diskread-only memory (CD-ROM), DVD, or a solid-state memory device. Thememory 206 holds instructions and data used by the processor 202. Thepointing device 214 is used in combination with the keyboard 210 toinput data into the computer system 200. The graphics adapter 212displays images and other information on the display device 218. In someembodiments, the display device 218 includes a touch screen capabilityfor receiving user input and selections. The network adapter 216 couplesthe computer system 200 to the network 110. Some embodiments of thecomputer 200 have different and/or other components than those shown inFIG. 2. For example, the global manager 120 and/or the managed server130 can be formed of multiple blade servers and lack a display device,keyboard, and other components, while the unmanaged device 140 can be anotebook or desktop computer, a tablet computer, or a mobile phone.

The computer 200 is adapted to execute computer program modules forproviding functionality described herein. As used herein, the term“module” refers to computer program instructions and/or other logic usedto provide the specified functionality. Thus, a module can beimplemented in hardware, firmware, and/or software. In one embodiment,program modules formed of executable computer program instructions arestored on the storage device 208, loaded into the memory 206, andexecuted by the processor 202.

FIG. 3 is a high-level block diagram illustrating a detailed view of aglobal manager 120, according to one embodiment. The global manager 120includes a repository 300 and a processing server 310. The repository300 is a computer (or set of computers) that stores the state of theadministrative domain's computer network infrastructure 320 and theadministrative domain-wide management policy 330. In one embodiment, therepository 300 includes a server that provides the processing server 310access to the administrative domain state 320 and the management policy330 in response to requests.

The state of the administrative domain's computer network infrastructure320 includes descriptions of managed servers 130 and (optionally)descriptions of unmanaged devices 140. A description of a managed server130 includes, for example, a unique identifier (UID), an online/offlineindicator, one or more configured characteristics (optional), networkexposure information, service information, and one or more labels thatdescribe the managed server 130 (a label set).

The UID uniquely identifies the managed server 130. The online/offlineindicator indicates whether the managed server 130 is online or offline.A “configured characteristic” stores a value associated with the managedserver 130 and can be any type of information (e.g., an indication ofwhich operating system is running on the managed server). A configuredcharacteristic is used in conjunction with a rule's condition portion(described below).

The network exposure information concerns the managed server's networkinterfaces. In one embodiment, the network exposure informationincludes, for each of the managed server's network interfaces, anidentifier of a “bidirectionally-reachable network” (BRN) to which thenetwork interface is attached and zero or more IP addresses (and theirsubnets) that are used for operating within the BRN. In anotherembodiment, the network exposure information includes routinginformation and/or whether the managed server is behind a networkaddress translator (NAT) (and, if it is behind a NAT, what type ofNAT—1:1 or 1:N). A BRN is a set of subnets, within an organization oracross organizations, where any node within the BRN can establishcommunication with any other node in the BRN. For example, all of thenodes in a BRN have unique IP addresses. In other words, a BRN does notcontain any NATs. Network exposure information (e.g., a networkinterface's BRN identifier) can be used in conjunction with a rule'scondition portion.

The service information includes, for example, process informationand/or package information. Process information includes, for example,names of processes that the managed server 130 is running, which networkports and network interfaces those processes are listening on, whichusers initiated those processes, configurations of those processes, andcommand-line launch arguments of those processes. (Those processescorrespond to the managed server 130 providing a service or using aservice.) Package information includes, for example, which packages(executables, libraries, or other components) are installed on themanaged server 130, the versions of those packages, the configurationsof those packages, and the hash values of those packages.

A description of an unmanaged device 140 includes, for example, networkexposure information (e.g., the IP address of the unmanaged device andan identifier of the BRN to which the unmanaged device is connected). Anunmanaged device 140 is part of an “unmanaged device group” (UDG). AnUDG includes one or more unmanaged devices 140. For example, the“Headquarters UDG” could include the primary circuit and the backupcircuit that are used by an administrative domain's headquarters, whereeach circuit is associated with an IP address. An UDG is associated witha unique identifier (UID). Information stored in the administrativedomain state 320 regarding an UDG includes the UID of the UDG andinformation regarding the unmanaged devices 140 in the UDG (e.g., theirnetwork exposure information).

Descriptions of managed servers 130 and unmanaged devices 140 can beloaded into the administrative domain state 320 in various ways, such asby interacting with the global manager 120 via a graphical userinterface (GUI) or an application programming interface (API).Descriptions of managed servers 130 can also be loaded into theadministrative domain state 320 based on local status informationreceived from managed servers (described below).

Regarding managed servers' labels specifically (and configuredcharacteristics, if any), the assignment (or reassignment) of a valuefor a dimension (or the setting of a configured characteristic's value)can be performed in even more ways. For example, the assignment/settingcan be performed using a deployment and configuration tool as part ofprovisioning a managed server 130. Any such tool can be used, includingoff-the-shelf third-party tools (e.g., Puppet Labs' Puppet software,Opscode's Chef software, or CFEngine AS' CFEngine software) and customtools that an administrative domain 150 might have.

As another example, the assignment/setting can be performed by a“label/configured characteristic engine” (not shown) that calculateslabels and/or configured characteristic (“CC”) values. In oneembodiment, the label/CC engine calculates labels/CC values based onlabel/CC assignment rules. A label/CC assignment rule is a function thataccesses data from the administrative domain state 320 and assigns (orsuggests assignment of) a label or a CC value. A label/CC assignmentrule can be preset or user-configurable. For example, the global manager120 includes a set of predefined rules, but the end-user can modifyand/or delete those rules and add new rules based on the user's owncustom requirements. Label/CC assignment rules can be evaluated for amanaged server 130 during the initialization process. Label/CC valuesuggestions can then be made for any dimension/CC, and the end-user canaccept or reject those suggestions. For example, if a managed server 130is executing the Postgres database or the MySQL database, then thesuggested label could be <Role, Database>. If a managed server isexecuting the Linux operating system, then the suggested value for theoperating system CC could be “Linux.”

In another embodiment, the label/CC engine calculates labels/CC valuesbased on cluster analysis. For example, the label/CC engine uses acombination of min-cut and K-means algorithms, with additionalheuristics, of connected graphs to automatically identify a cluster ofhighly-connected managed servers 130. The cluster of managed servers 130might correspond to an “application” (see Table 1) in the administrativedomain 150. The end-user can choose to apply a value for the Applicationdimension (or any other dimension) to those managed servers 130 enmasse.

The administrative domain-wide management policy 330 includes one ormore rules. Broadly speaking, a “rule” specifies a relationship betweenone or more providers of a service and one or more consumers of thatservice.

Rule Function—The relationship is subjected to a “rule function”, whichis the practical effect of the rule. For example, in the case ofsecurity, the rule function could be access control, secureconnectivity, disk encryption, or control of executable processes. Arule with an access control function specifies whether a consumer mayuse a provider's service. In one embodiment, the access control functionuses a pure “whitelist” model, which means that only the allowablerelationships are expressed, and all other relationships are blocked bydefault. A rule with a secure connectivity function specifies over whatsecure channels (e.g., encrypted network sessions using point-to-pointdata encryption) a consumer may use a provider's service. For example, arule with a secure connectivity function could specify that usage of aprovider's services must be encrypted when the provider is located inthe US and the consumer is located in the EU. A rule with a diskencryption function specifies whether a provider must store its data onan encrypted file system. A rule with an executable process-controlfunction specifies whether a provider must execute on an encrypted filesystem.

In the case of resource usage, the rule function could be disk-usage orperipheral-usage. A rule with a disk-usage function specifies an amountof data that a consumer can store on a provider. Note that a rule canspecify other rule functions as well beyond just access control, secureconnectivity, disk encryption, control of executable processes, diskusage, and peripheral usage. For example, a rule function could specifywhich Open Systems Interconnection (OSI) model Layer-7 services to applyto network traffic, the amount of metadata to collect for securityanalytics, or the triggers for capturing a complete network packet. Themanagement policy model supports any number of rule functions that canbe applied.

A rule function can be associated with one or more settings (referred toherein as a “function profile”) that specify details regarding thepractical effect of the rule. For example, settings associated with asecure connectivity rule function can be a list of cryptographicalgorithms used to encrypt network traffic. In one embodiment, a rulefunction is associated with multiple function profiles, and a functionprofile includes a priority. This priority is used by the function-levelinstruction generation module 360, as described below.

Service—In general, a “service” is an arbitrary process executing on aspecific network port using a specific network protocol. A service of arule within the management policy 330 is specified by a port/protocolpair and (optionally) additional qualifications, such as processinformation and/or package information (described above with respect toa description of a managed server 130 within the administrative domainstate 320). If a managed server 130 has multiple network interfaces,then a service can be exposed on all networks or on only a subset ofthose networks. The end-user specifies on which networks the service isexposed.

Providers/Consumers—The one or more providers of the service and the oneor more consumers (i.e., users) of the service are managed servers 130and/or unmanaged devices 140.

In one embodiment, a rule is represented within the administrativedomain-wide management policy 330 using a set of information thatincludes a rule function portion, a service portion, a provided-byportion, a used-by portion, and an optional rule condition portion. Therule function portion describes the practical effect of the rule and canbe associated with one or more settings (function profiles). The serviceportion describes the service to which the rule applies. If the serviceportion indicates “All”, then the rule applies to all services.

The provided-by (PB) portion describes which managed servers 130 and/orunmanaged devices 140 can provide the service (i.e., who the “providers”are). If the PB portion indicates “Anybody”, then anybody (e.g., anymanaged server 130 or unmanaged device 140) can provide the service. Ifthe PB portion indicates “Any managed server”, then any managed server130 can provide the service. (“Any managed server” is equivalent tospecifying a label set that contains a wildcard, thereby matching allmanaged servers 130.) The used-by (UB) portion describes which managedservers 130 and/or unmanaged devices 140 can use the service (i.e., whothe “consumers” are). Similar to the PB portion, the UB portion can alsoindicate “Anybody” or “Any managed server.”

Within the PB portion and the UB portion, a managed server 130 isspecified by using a label set (i.e., one or more labels that describethe managed server) or a UID. The ability to specify managed servers 130using label sets stems from the logical management model, whichreferences managed servers based on their dimensions and values(labels). An unmanaged device 140 is specified by using a UID of anunmanaged device group (UDG). If a rule specifies an UDG, then the ruleincludes additional information regarding the unmanaged devices 140 inthat group (e.g., the devices' network exposure information). The PBportion of a rule and/or the UB portion of a rule can include multipleitems, including label sets (to specify managed servers 130), managedserver UIDs, and/or UDG UIDs.

The rule condition portion, which is optional, specifies whether therule applies to a particular managed server 130 and/or a particularnetwork interface of that managed server. The rule condition portion isa Boolean expression that includes one or more configuredcharacteristics (“CCs”; part of a managed server's description in theadministrative domain state 320) and/or network exposure information(e.g., a network interface's BRN identifier; also part of a managedserver's description in the administrative domain state 320). A CCportion of the expression specifies whether the rule applies to theparticular managed server, while a network exposure information portionof the expression specifies whether the rule applies to a particularnetwork interface of that managed server. If the expression evaluates to“true” for a particular managed server's configured characteristics(specifically, for the values of that managed server's configuredcharacteristics) and a particular network interface's information, thenthe rule applies to that managed server and that managed server'srelevant network interface. If the expression evaluates to “false”, thenthe rule does not apply to that managed server and that managed server'srelevant network interface. For example, if a configured characteristicstores an indication of which operating system is running on the managedserver, then a rule condition portion that includes that configuredcharacteristic can control whether the rule applies to a particularmanaged server based on that server's operating system.

Rules within the administrative domain-wide management policy 330 areorganized into rule lists. Specifically, the management policy 330includes one or more rule lists, and a rule list includes one or morerules and (optionally) one or more scopes. A “scope” constrains where(i.e., to which managed servers 130) a rule is applied. A scope includesa provided-by (PB) portion and a used-by (UB) portion that limit theapplication of the rules in the rule list. The PB portion of the scopelimits the PB portion of the rules, and the UB portion of the scopelimits the UB portion of the rules. The PB and UB portions of a scopecan specify a group of managed servers 130 by using a label set. If thelabel set does not contain a label for a specific dimension, then thereis no scoping of that dimension for the resulting group of managedservers 130. If a rule list does not include any scopes, then its rulesare applied globally.

Different scopes can be applied to a single rule list. For example, anend-user can build a set of rules that express how the web service tierconsumes services from the database tier, how the load-balancing tierconsumes services from the web service tier, and so on. Then, if theend-user wants to apply this rule list to his production environment andto his staging environment, he does not need to copy or duplicate therule list. Instead, he applies multiple scopes to a single rule list.The scope abstraction makes the rule list scale from both a usabilityperspective and a computational perspective.

Now that the administrative domain-wide management policy 330 has beendescribed, it is helpful to work through some examples. Consider anadministrative domain 150 with a two-tier application where a userdevice accesses a web server (the first tier), and the web serveraccesses a database server (the second tier). In the first tier, theuser device is the consumer, and the web server is the provider. In thesecond tier, the web server is the consumer, and the database server isthe provider. The administrative domain 150 includes two instances ofthis application: one in a production environment and one in a stagingenvironment.

The web servers and the database servers are managed servers 130, andtheir descriptions (e.g., label sets) are present in the administrativedomain state 320. For example, their label sets are:

web server in production: <Role, Web> and <Environment, Production>database server in production: <Role, Database> and <Environment,Production>web server in staging: <Role, Web> and <Environment, Staging>database server in staging: <Role, Database> and <Environment, Staging>(The Application dimension, the Line of Business dimension, and theLocation dimension are not relevant to this example, so their labels areomitted.)

Now consider the following administrative domain-wide management policy330, which is a security policy that specifies access control and secureconnectivity:

Rule List #1

Scopes

-   -   <Environment, Production>    -   <Environment, Staging>

Rules

-   -   #1        -   Function: Access Control        -   Service: Apache        -   PB: <Role, Web>        -   UB: Anybody    -   #2        -   Function: Access Control        -   Service: PostgreSQL        -   PB: <Role, Database>        -   UB: <Role, Web>

Rule List #2

Scopes: None

Rules

-   -   #1        -   Function: Secure Connectivity        -   Service: All        -   PB: <Role, Database>        -   UB: Any managed server

Note that the rules above refer to services simply as “Apache” and“PostgreSQL” for clarity. Remember that a service is a process and isspecified by a port/protocol pair and (optionally) additionalqualifications, such as process information and/or package information(described above with respect to a description of a managed server 130within the administrative domain state 320).

Rule List #1/Rule #1 allows any device (e.g., a user device) to connectto a web server and use the Apache service. Specifically, the allowanceof a connection is specified by “Access Control” in the Functionportion. The “any device” is specified by “Anybody” in the UB portion.The “web server” is specified by “<Role, Web>” (a label set thatincludes only one label) in the PB portion. The Apache service isspecified by “Apache” in the Service portion.

Rule List #1/Rule #2 allows a web server to connect to PostgreSQL on adatabase server. Specifically, the allowance of a connection isspecified by “Access Control” in the Function portion. The “web server”is specified by “<Role, Web>” in the UB portion. The “PostgreSQL” isspecified by “PostgreSQL” in the Service portion. The “database server”is specified by “<Role, Database>” (a label set that includes only onelabel) in the PB portion.

Rule List #1 also prevents inter-environment connections. For example, aweb server is allowed to connect to PostgreSQL on a database server ifthe web server and database server are both in the same environment(e.g., both in the production environment or both in the stagingenvironment). Both servers in the production environment is specified by“<Environment, Production>” (a label set that includes only one label)in the Scope portion, while both servers in the staging environment isspecified by “<Environment, Staging>” (a label set that includes onlyone label) in the Scope portion. As a result, a web server is notallowed to connect to PostgreSQL on a database server if the servers arein different environments (e.g., if the web server is in the stagingenvironment, and the database server is in the production environment).

Rule List #2 states that whenever any managed server connects to adatabase server, that connection must be performed through an encryptedchannel. Specifically, the “database server” is specified by “<Role,Database>” in the PB portion. The “encrypted channel” is specified by“Secure Connectivity” in the Function portion. The “any managed server”is specified by “Any managed server” in the UB portion. The “whenever”is specified by “All” in the Service portion.

Turning aside from the above example, consider the following two managedservers 130: Server 1 is a web server that is part of production, partof app1, and owned by engineering in California. It would be labeled as:

<Role, Web> <Environment, Production>

<Application, app1>

<LB, Engineering> <Location, US>

Server 2 is a database server that is part of production, also part ofapp1, and also owned by engineering but in Germany. It would be labeledas:

<Role, Database Server> <Environment, Production>

<Application, app1>

<LB, Engineering> <Location, EU>

Assume that an access control rule allows all access to all managedservers 130 that are part of app1. This rule would allow Server 1 andServer 2 to communicate with each other and would disallow a managedserver 130 in Germany that is part of app2 from communicating withServer 1 or Server 2. Now assume that a secure connectivity rulespecifies that all network traffic between EU and US must be encrypted.Rule functions are independently applied. In other words, the secureconnectivity rule is a separate policy that is applied independent ofthe access control rule. As a result, the network traffic from Server 1to Server 2 would be allowed (given the access control rule) andencrypted (given the secure connectivity rule).

Returning to FIG. 3, the processing server 310 generates managementinstructions for managed servers 130 and sends the generated managementinstructions to the servers. The processing server 310 also processeslocal state information received from managed servers 130. Theprocessing server 310 includes various modules such as a policy enginemodule 340, a relevant rules module 350, a function-level instructiongeneration module 360, an actor enumeration module 370, a relevantactors module 380, and an administrative domain state update module 385.In one embodiment, the processing server 310 includes a computer (or setof computers) that communicates with the repository 300 and processesdata (e.g., by executing the policy engine module 340, the relevantrules module 350, the function-level instruction generation module 360,the actor enumeration module 370, the relevant actors module 380, andthe administrative domain state update module 385).

The relevant rules module 350 takes as input the administrativedomain-wide management policy 330 and an indication of a particularmanaged server 130 (e.g., that server's UID) generates a set of rulesthat are relevant to that server, and outputs the set of rules. This isa filtering process by which the relevant rules module 350 examines themanagement policy 330 and extracts only the relevant rules for the givenmanaged server 130. The relevant rules module 350 performs the filteringby iterating through all of the rule lists in the management policy 330,analyzing the scopes of each rule list to determine whether the scopesapply to this managed server 130 and (if the scopes do apply to thismanaged server 130) analyzing the rules of each rule list to determinewhether those rules apply to this managed server 130. A rule applies toa managed server 130 if a) the PB portion of the rule and/or the UBportion of the rule specifies the managed server and b) the conditionportion of the rule (if present) evaluates to “true” for that managedserver (specifically, for the values of that managed server's configuredcharacteristics and network exposure information). The end result(referred to herein as a “management policy perspective”) is acollection of two sets of rules: rules where this managed server 130provides a service and rules where this managed server 130 consumes aservice.

The function-level instruction generation module 360 takes as input aset of rules (e.g., a management policy perspective generated by therelevant rules module 350), generates function-level instructions, andoutputs the function-level instructions. The function-level instructionsare later sent to a managed server 130 as part of the managementinstructions. A function-level instruction is similar to a rule in thateach one includes a rule function portion, a service portion, a PBportion, and a UB portion. However, whereas a rule can include multipleitems within its PB portion and/or UB portion (including label sets,managed server UIDs, and/or UDG UIDs), a function-level instructionincludes only one item within its PB portion and only one item withinits UB portion. Also, whereas a rule can specify a managed server(including its multiple network interfaces) within its PB portion and/orUB portion, a function-level instruction includes only one networkinterface within its PB portion and UB portion.

The function-level instruction generation module 360 analyzes a rule andgenerates one or more function-level instructions based on that rule. Ifthe rule's PB portion includes multiple items, the rule's UB portionincludes multiple items, or a managed server referenced by the rule (inthe PB portion or UB portion) has multiple network interfaces, then thefunction-level instruction generation module 360 generates multiplefunction-level instructions (e.g., one function-level instruction foreach possible combination of a PB item, a UB item, and a particularnetwork interface).

Consider a rule that includes two items in its PB portion (A and B) andtwo items in its UB portion (C and D). The function-level instructiongeneration module 360 would generate four function-level instructionswith the following PB and UB portions: 1) PB=A, UB=C; 2) PB=A, UB=D; 3)PB=B, UB=C; 4) PB=B, UB=D. Now consider a rule that covers a managedserver in its PB portion or UB portion (e.g., by specifying a UID or alabel set), and that managed server has multiple network interfaces. Thefunction-level instruction generation module 360 would generate multiplefunction-level instructions (e.g., one function-level instruction foreach network interface of the managed server).

The function-level instruction generation module 360 analyzes the rules,the functions within those rules, and the function profiles referencedby those rules. If a rule list includes multiple scopes, then thefunction-level instruction generation module 360 applies those scopesmultiple times to the rule list iteratively (thereby generating acomplete set of function-level instructions for each scope). Recall thata rule function can be associated with multiple function profiles, and afunction profile can include a priority. The function-level instructiongeneration module 360 orders the rules based on the priorities of thevarious function profiles such that the function profile with thehighest priority is used. The function-level instruction generationmodule 360 translates the ordered rules into function-level instructionsfor the managed server 130 to execute. Function-level instructionsreference the appropriate managed servers 130 and/or unmanaged devices140 (e.g., the managed servers 130 and/or unmanaged devices 140 thatwere referenced in the input rules), taking into account the networkexposure details of the services associated with the rules.

Note that the function-level instruction generation module 360 cangenerate a function-level instruction for a particular managed server130 that turns out to be irrelevant for that server. For example, thatmanaged server is covered by the provided-by (PB) portion of a rule, sothe function-level instruction generation module 360 generates acorresponding function-level instruction. However, the rule alsoincludes a portion that specifies the managed server's local state(e.g., a service portion that describes the provided service). Since theglobal manager 120 does not know the managed server's local state (e.g.,whether the managed server is actually providing that service), thegenerated function-level instruction is sent to the managed server. Themanaged server checks its local state (e.g., whether it is providingthat service) and processes the function-level instruction accordingly,as explained below with reference to the policy compilation module 410.

The actor enumeration module 370 takes as input a collection ofdescriptions of managed servers 130 and unmanaged device groups (UDGs)(e.g., the state of the administrative domain's computer networkinfrastructure 320), generates representations of those descriptions ofservers and UDGs in an enumerated form (referred to as “actor-sets”),and outputs the actor-sets. For example, the actor enumeration module370 enumerates the managed servers 130 and the UDGs within theadministrative domain state 320 and the possible label sets and assignseach a unique identifier (UID). These actor-sets can then be used inconjunction with UB portions and PB portions of rules and scopes, whichspecify actors using managed server UIDs, UDG UIDs, and/or label sets.

Consider a logical management model that includes a set of N dimensionsD_(i) (i=1, . . . , N), and each dimension D_(i) includes a set S_(i) ofpossible values V_(j) (j=1, . . . , M_(i)) (where the wildcard “*” isone of the possible values). In one embodiment, the actor enumerationmodule 370 enumerates all label sets that are possible based on thelogical management model, which are equal to the Cartesian product givenby S₁×S₂× . . . ×S_(N). The size of this set is M₁×M₂× . . . ×M_(N). Theenumeration process collapses the multi-dimensional label space of themanaged servers 130 into a simple enumerated form.

In another embodiment, the actor enumeration module 370 enumerates onlythose label sets that are possible based on the administrative domainstate 320 (e.g., based on descriptions of managed servers within theadministrative domain 150). For example, consider a logical managementmodel that includes 2 dimensions (X and Y), and each dimension includes3 possible values (A, B, and *). A managed server with the label set“<X=A>,<Y=B>” can be a member of 4 possible label sets: 1)“<X=A>,<Y=B>”, 2) “<X=A>,<Y=*>”, 3) “<X=*>,<Y=B>”, and 4) “<X=*>,<Y=*>”.Note that the managed server's label set exists in 2-dimensional space(X and Y), while possible label sets 2, 3, and 4 are projections of themanaged server's label set into sub-dimensional spaces (label set 2 is1-dimensional space (X), label set 3 is 1-dimensional space (Y), andlabel set 4 is 0-dimensional space). So, the actor enumeration module370 enumerates those 4 possible label sets. The managed server with thelabel set “<X=A>,<Y=B>” cannot be a member of the label set“<X=A>,<Y=A>”, so the actor enumeration module 370 does not enumeratethat label set.

An actor-set includes a UID and zero or more actor-set records. Anactor-set record includes a UID (either a managed server UID or an UDGUID), an identifier of the actor's operating system, and the IP addressof the actor (managed server 130 or unmanaged device 140) given thespecific BRN. For example, an actor-set might include actor-set recordswhose IP addresses correspond to all of the managed servers 130 coveredby the label set of <Role, Database> and <Environment, Production>. Asanother example, an actor-set might include actor-set records whose IPaddresses correspond to all of the unmanaged devices 140 in theHeadquarters UDG. A single actor (e.g., managed server 130 or unmanageddevice 140) can appear in multiple actor-sets.

Another factor in the actor-set calculation is actors with multiplenetwork interfaces, plus the inclusion of network topology such asnetwork address translation (NAT). So, there could be two actor-sets forthe label set of <Role, Database> and <Environment, Production>: oneactor-set with the internet-facing IP addresses of those managed servers130 (i.e., associated with a first BRN), and a different actor-set forthose same managed servers with the private network-facing IP addressesof those managed servers (i.e., associated with a second BRN).

In one embodiment, the actor enumeration module 370 can also updateactor-sets based on changes to the administrative domain's state 320.For example, the actor enumeration module 370 takes as input actor-sets(previously output by the actor enumeration module) and a change to amanaged server's description (within the administrative domain state320), generates updated actor-sets (which are consistent with thechanged server description), and outputs the updated actor-sets. Theactor enumeration module 370 generates the updated actor-sets indifferent ways depending on the type of change to the managed server'sdescription.

Offline/online change—If the description change indicates that theserver went from online to offline, then the actor enumeration module370 generates the updated actor-sets by removing the server's actor-setrecord from all input actor-sets of which the server was a member. Ifthe description change indicates that the server went from offline toonline, then the actor enumeration module 370 generates the updatedactor-sets by adding the server's actor-set record to any relevant inputactor-sets. (If necessary, the actor enumeration module 370 creates anew actor-set and adds the server's actor-set record to that newactor-set.)

Label set change—If the description change indicates that the server'slabel set changed, then the actor enumeration module 370 treats thislike a first server (with the old label set) going offline and a secondserver (with the new label set) coming online.

Network exposure information change—If the description change indicatesthat the server removed a network interface, then the actor enumerationmodule 370 generates the updated actor-sets by removing the server'sactor-set record from all input actor-sets (associated with that networkinterface's BRN) of which the server was a member. If the descriptionchange indicates that the server added a network interface, then theactor enumeration module 370 generates the updated actor-sets by addingthe server's actor-set record to any relevant input actor-sets(associated with that network interface's BRN). (If necessary, the actorenumeration module 370 creates a new actor-set (associated with thatnetwork interface's BRN) and adds the server's actor-set record to thatnew actor-set.) If the description change indicates that the serverchanged a network interface's BRN, then the actor enumeration module 370treats this like a first network interface (with the old BRN) beingremoved and a second network interface (with the new BRN) being added.If the description change indicates that the server changed a networkinterface's IP address (but not the BRN), then the actor enumerationmodule 370 generates the updated actor-sets by modifying the server'sactor-set record in all input actor-sets (associated with that networkinterface's BRN) of which the server was a member.

The relevant actors module 380 takes as input one or more actor-sets(e.g., the managed servers 130 and the UDGs within the administrativedomain state 320 in enumerated form) and a set of rules (e.g., amanagement policy perspective), determines which actor-sets are relevantto those rules, and outputs only those actor-sets. This is a filteringprocess by which the relevant actors module 380 examines the actor-setsand extracts only the relevant actor-sets for the given set of rules.The relevant actors module 380 performs the filtering by iteratingthrough all of the input actor-sets, analyzing the PB portions and UBportions of the input rules to determine whether a particular actor-setis referenced by any of the rules' PB portions or UB portions. The endresult (referred to herein as an “actor perspective”) is a collection ofactor-sets. The actor perspective is later sent to a managed server 130as part of the management instructions.

In one embodiment, the relevant actors module 380 uses the input set ofrules to generate an “actor-set filter.” The actor-set filter selects,from the input actor-sets, only the actor-sets that are relevant to theinput rules. In other words, the relevant actors module 380 uses theactor-set filter to filter the input actor-sets into relevantactor-sets.

The policy engine module 340 generates management instructions formanaged servers 130 and sends the generated management instructions tothe servers. The policy engine module 340 generates the managementinstructions (using the relevant rules module 350, the function-levelinstruction generation module 360, the actor enumeration module 370, andthe relevant actors module 380) based on a) the state of theadministrative domain's computer network infrastructure 320 and b) theadministrative domain-wide management policy 330.

For example, the policy engine module 340 executes the relevant rulesmodule 350, providing as input the administrative domain-wide managementpolicy 330 and the UID of a particular managed server 130. The relevantrules module 350 outputs a set of rules that are relevant to that server(a “management policy perspective”). The policy engine module 340executes the actor enumeration module 370, providing as input theadministrative domain state 320. The actor enumeration module 370outputs a representation of the descriptions of the managed servers 130and unmanaged device groups (UDGs) within the administrative domainstate 320 in an enumerated form (“actor-sets”). The policy engine module340 executes the function-level instruction generation module 360,providing as input the management policy perspective (output by therelevant rules module 350). The function-level instruction generationmodule 360 outputs function-level instructions. The policy engine module340 executes the relevant actors module 380, providing as input theactor-sets (output by the enumeration module 370) and the managementpolicy perspective (output by the relevant rules module 350). Therelevant actors module 380 outputs only those actor-sets that arerelevant to those rules (“relevant actor-sets”). The policy enginemodule 340 sends the function-level instructions (output by thefunction-level instruction generation module 360) and the relevantactor-sets (output by the relevant actors module 380) to the particularmanaged server 130.

In one embodiment, the policy engine module 340 caches information thatwas generated during the above process. For example, the policy enginemodule 340 caches, in association with the particular managed server130, the management policy perspective, the function-level instructions,the actor-set filter, and/or the relevant actor-sets. As anotherexample, the policy engine module 340 caches the actor-sets (which arenot specific to a particular managed server 130).

Since an administrative domain's actor-sets are based on theadministrative domain state 320, a change to the administrative domainstate 320 can require a change to the administrative domain'sactor-sets. Similarly, since a managed server's management instructionsare based on the administrative domain state 320 and the administrativedomain-wide management policy 330, a change to the administrative domainstate 320 and/or a change to the administrative domain-wide managementpolicy 330 can require a change to the managed server's managementinstructions. In one embodiment, the policy engine module 340 can updatean administrative domain's actor-sets and/or update a managed server'smanagement instructions and then distribute these changes (if necessary)to managed servers 130. The cached information mentioned above helps thepolicy engine module 340 more efficiently update the administrativedomain's actor-sets and/or the managed server's management instructionsand distribute the changes.

In one embodiment, the policy engine module 340 updates anadministrative domain's actor-sets (based on a change to theadministrative domain state 320) and distributes the changes to managedservers 130 as follows: The policy engine module 340 executes the actorenumeration module 370, providing as input the cached actor-sets(previously output by the actor enumeration module) and the changedportion of the administrative domain state 320 (i.e., the changed serverdescription). The actor enumeration module 370 outputs the updatedactor-sets. In one embodiment, the policy engine module 340 then sendsall of the updated actor-sets to all of the managed servers 130 withinthe administrative domain 150. However, that embodiment is inefficient,since not all managed servers are affected by changes to all actor-sets.

In another embodiment, only selected actor-sets are sent to selectedservers. For example, a particular managed server is sent only thoseactor-sets that a) were previously sent to that server and b) havechanged. The cached relevant actor-sets indicate which actor-sets werepreviously sent to that server (see (a) above). The policy engine module340 compares the cached actor-sets to the updated actor-sets todetermine which actor-sets have changed (see (b) above). The policyengine module 340 then computes the intersection of (a) and (b).Actor-sets in that intersection are sent to the particular managedserver. In one embodiment, for even greater efficiency, actor-sets aresent in “diff” format. For example, the diff format specifies anactor-set identifier, an actor identifier (e.g., a managed server UID oran UDG UID), and an indication of whether that actor should be added,removed, or modified.

In yet another embodiment, two tables are maintained and used to improveefficiency. A first table associates a managed server 130 withactor-sets of which that managed server is a member. A second tableassociates a managed server 130 with actor-sets that are relevant tothat managed server (e.g., as determined by the relevant actors module380). In these tables, a managed server 130 is represented by, e.g.,that managed server's UID, and an actor-set is represented by, e.g.,that actor-set's UID. The policy engine module 340 uses the changedportion of the administrative domain state 320 (i.e., the changed serverdescription) to determine which managed server's description changed.The policy engine module 340 uses the first table to determine whichactor-sets that managed server was a member of Those actor-sets mightchange as a result of the changed server description. So, the policyengine module 340 uses the second table to determine which managedservers those actor-sets are relevant to. The policy engine module 340performs the intersection computation described above for only thosemanaged servers.

In one embodiment, the policy engine module 340 updates a managedserver's management instructions (based on a change to theadministrative domain state 320) and sends the updated managementinstructions to the managed server as follows: The policy engine module340 executes the relevant rules module 350, providing as input theadministrative domain-wide management policy 330 and the UID of themanaged server 130. The relevant rules module 350 outputs a set of rulesthat are relevant to that server (a “management policy perspective”).The policy engine module 340 compares the management policy perspectivethat was just output to the cached management policy perspective todetermine whether they differ. If the just-output management policyperspective and the cached management policy perspective are identical,then the policy engine module 340 takes no further action. In thissituation, the previously-generated managed server's managementinstructions (specifically, the function-level instructions and relevantactor-sets) are consistent with the change to the administrative domainstate 320 and do not need to be re-generated and re-sent to the managedserver.

If the just-output management policy perspective and the cachedmanagement policy perspective differ, then the policy engine module 340determines which rules should be added to the cached perspective andwhich rules should be removed from the cached perspective. The policyengine module 340 executes the function-level instruction generationmodule 360, providing as input the rules to add and the rules to remove.The function-level instruction generation module 360 outputsfunction-level instructions to add and function-level instructions toremove (relative to the cached function-level instructions, which werepreviously sent to the managed server). The policy engine module 340instructs the managed server to add or remove the various function-levelinstructions, as appropriate. In one embodiment, for greater efficiency,function-level instructions are sent in “diff” format. For example, thediff format specifies a function-level instruction identifier and anindication of whether that function-level instruction should be added toor removed from the previously-sent function-level instructions.

The policy engine module 340 also executes the actor enumeration module370, providing as input the cached actor-sets and the changed portion ofthe administrative domain state 320 (i.e., the changed serverdescription). The actor enumeration module 370 outputs the updatedactor-sets. The policy engine module 340 executes the relevant actorsmodule 380, providing as input the updated actor-sets and thejust-output management policy perspective. The relevant actors module380 outputs only those updated actor-sets that are relevant to thoserules (“updated relevant actor-sets”).

The policy engine module 340 compares the updated relevant actor-sets tothe cached relevant actor-sets to determine whether they differ. If theupdated relevant actor-sets and the cached relevant actor-sets areidentical, then the policy engine module 340 sends no actor-sets to themanaged server. In this situation, the previously-generated relevantactor-sets are consistent with the change to the administrative domainstate 320 and do not need to be re-sent to the managed server. If theupdated relevant actor-sets and the cached relevant actor-sets differ,then the policy engine module 340 determines which actor-sets should beadded, removed, or modified relative to the cached relevant actor-sets.The policy engine module 340 instructs the managed server to add,remove, or modify the various actor-sets, as appropriate. In oneembodiment, for greater efficiency, actor-sets are sent in “diff”format. For example, the diff format specifies an actor-set identifierand an indication of whether that actor-set should be added, removed, ormodified relative to the previously-sent actor-sets.

Recall that the policy engine module 340 can update a managed server'smanagement instructions (based on a change to the administrativedomain-wide management policy 330) and send the updated managementinstructions to the managed server. A change to the management policy330 is, for example, the addition, removal, or modification of a rule ora rule set. In one embodiment, a change to the management policy 330 isgenerated by interaction with the global manager 120 via a GUI or API.In another embodiment, a change to the management policy 330 isgenerated by an automated process within the global manager 120 (e.g.,in response to a security threat detected by the global manager). Thepolicy engine module 340 updates the managed server's managementinstructions and sends the updated management instructions to themanaged server in a similar way, regardless of whether there was achange to the management policy 330 or a change to the administrativedomain state 320. However, there are a few differences.

In the case of a change to the management policy 330, the policy enginemodule 340 does not necessarily update management instructions for allmanaged servers 130. Instead, the policy engine module 340 compares theprevious management policy 330 to the new management policy 330 todetermine which rules should be added, removed, or modified relative tothe previous management policy 330. The policy engine module 340determines which managed servers 130 are affected by the changed rules(e.g., which managed servers are covered by a) the rules' and/or scopes'PB and/or UB portions and b) the rules' conditional portions (if any)).The policy engine module 340 executes the relevant rules module 350,providing as input the changed rules (instead of the entire newmanagement policy 330) and the UID of the managed server 130 (for onlythose servers that are affected by the changed rules)

The administrative domain state update (ADSU) module 385 receiveschanges to the administrative domain state 320 and processes thosechanges. A change to the administrative domain state 320 is, forexample, the addition, removal, or modification of a description of amanaged server 130 (including the modification of a managed server'slabel set or configured characteristics) or a description of anunmanaged device or unmanaged device group. In one embodiment, a changeto the administrative domain state 320 originates in local stateinformation received from a particular managed server 130. In anotherembodiment, a change to the administrative domain state 320 is generatedby interaction with the global manager 120 via a GUI or API. In yetanother embodiment, a change to the administrative domain state 320 isgenerated by an automated process within the global manager 120 (e.g.,in response to a security threat detected by the global manager).

For example, the ADSU module 385 receives a change regarding aparticular managed server 130. The ADSU module 385 stores the newinformation in the administrative domain state 320 as part of thedescription of that particular managed server 130. The ADSU module 385then (optionally) analyzes that managed server's description todetermine additional information regarding the server and stores thatinformation in the description. The ADSU module 385 then determineswhether to update the administrative domain's actor-sets and/or themanaged server's management instructions based on a change to themanaged server's description. If the ADSU module 385 determines toupdate the administrative domain's actor-sets, then the ADSU module 385instructs the policy engine module 340 to update the administrativedomain's actor-sets. In one embodiment, the ADSU module 385 waits for anevent to occur before instructing the policy engine module 340 to updatethe administrative domain's actor-sets. If the ADSU module 385determines to update the managed server's management instructions, thenthe ADSU module 385 instructs the policy engine module 340 to update themanaged server's management instructions. In one embodiment, the ADSUmodule 385 waits for an event to occur before instructing the policyengine module 340 to update the managed server's managementinstructions. The aforementioned events can be, for example, receipt ofa user command or occurrence of a specified maintenance window.

Whether or not the ADSU module 385 determines to update theadministrative domain's actor-sets and/or the managed server'smanagement instructions depends on the type of change to the managedserver's description. In one embodiment, the ADSU module 385 makes thisdetermination as shown in Table 2:

TABLE 2 Whether to update administrative domain's actor-sets and/ormanaged server's management instructions based on type of serverdescription change Type of Change Whether to Update Online to offlineAdministrative domain's actor-sets: Yes Managed server's managementinstructions: No Offline to online Administrative domain's actor-sets:Yes Managed server's management instructions: Yes Label setAdministrative domain's actor-sets: Yes Managed server's managementinstructions: Yes Configured Administrative domain's actor-sets: Nocharacteristic Managed server's management instructions: Yes Networkexposure Administrative domain's actor-sets: Yes info Managed server'smanagement instructions: Yes (unless IP address is the only change)Service info Administrative domain's actor-sets: No Managed server'smanagement instructions: Yes (only in specified situations)

In one embodiment, the ADSU module 385 determines additional informationregarding the server by executing the label/configured characteristicengine and providing the server's description as input. The label/CCengine calculates labels/CC values for the server based on the server'sdescription and label/CC assignment rules.

In another embodiment, the ADSU module 385 determines whether the serveris behind a network address translator (NAT) (and, if it is behind aNAT, what type of NAT—1:1 or 1:N). For example, the ADSU module 385determines whether a NAT exists between the global manager 120 and themanaged server 130 by comparing (a) the server's IP address according tothe TCP connection between the global manager and the server and (b) theserver's IP address according to the local state information receivedfrom the server. If (a) and (b) differ, then a NAT exists between theglobal manager 120 and the managed server 130. If a NAT does exist, thenthe ADSU module 385 determines the type of NAT (1:1 or 1:N) byperforming data center detection. For example, the ADSU module 385identifies the server's data center by the data center's public IPaddress. (Alternatively, the managed server performs data centerdetection by querying information that is external to the server butinside the data center. The server then sends that information to theglobal manager as part of the local status.) Configuration informationindicates which types of NATs are used by which data centers. If no NATinformation is associated with a particular data center, then the ADSUmodule 385 assumes that the NAT type is 1:N.

FIG. 4 is a high-level block diagram illustrating a detailed view of apolicy implementation module 136 of a managed server 130, according toone embodiment. The policy implementation module 136 includes a localstate repository 400, a policy compilation module 410, and a local stateupdate module 420. The local state repository 400 stores informationregarding the local state of the managed server 130. In one embodiment,the local state repository 400 stores information regarding the managedserver's operating system (OS), network exposure, and services. OSinformation includes, for example, an indication of which OS is running.Network exposure information and service information were describedabove with respect to a description of a managed server 130 within theadministrative domain state 320.

The policy compilation module 410 takes as input management instructionsand state of a managed server 130 and generates a management moduleconfiguration 134. For example, the management instructions are receivedfrom the global manager 120 and include function-level instructions(generated by the function-level instruction generation module 360) andrelevant actor-sets (output by the relevant actors module 380). Thestate of the managed server 130 is retrieved from the local staterepository 400. In one embodiment, execution of the policy compilationmodule 410 is triggered by a) the managed server powering up or comingonline, b) the managed server receiving function-level instructions,and/or c) the contents of the local state repository 400 changing.

The policy compilation module 410 maps the function-level instructionsand relevant actor-sets into a management module configuration 134. Forexample, the policy compilation module 410 maps an access controlfunction-level instruction (which contains a port and an actor-setreference) into an iptables entry and an ipset entry in the Linuxoperating system or a Windows Filtering Platform (WFP) rule in theWindows operating system.

The application of management policy at a managed server 130 can beaffected by the local state of that server. In one embodiment, thepolicy compilation module 410 evaluates a condition associated with areceived function-level instruction and generates the management moduleconfiguration 134 based on the result of that evaluation. For example,the policy compilation module 410 evaluates a condition that referencesthe operating system of the managed server's peer (i.e., the other actorin the relationship) and selects function profile attributes based onthe result of that evaluation, where the selected function profileattributes are expressed in the management module configuration 134.

As another example, recall that a managed server 130 can receive afunction-level instruction that turns out to be irrelevant for thatserver. For example, the rule includes a portion that specifies themanaged server's local state (e.g., a service portion that describes theprovided service). Since the global manager 120 does not know themanaged server's local state (e.g., whether the managed server isactually providing that service), the generated function-levelinstruction is sent to the managed server. The policy compilation module410 checks the managed server's local state (e.g., determines whetherthe managed server is providing that service). This determinationamounts to evaluating a condition that references the managed server'slocal state. The policy compilation module 410 processes thefunction-level instruction accordingly. If the policy compilation module410 determines that the condition evaluates to “true” (e.g., the managedserver is providing that service), then the policy compilation module410 incorporates that function-level instruction into the managementmodule configuration 134. Specifically, the policy compilation module410 incorporates function-level instructions into the management moduleconfiguration 134 only after evaluating the associated condition (whichconcerns the local state of that server). If the evaluation of thecondition is false, then the policy compilation module 410 does notexpress the function-level instructions in the management moduleconfiguration 134. The specific conditions (e.g., their nature andparticular values) are extensible. In one embodiment, the conditions arerelated to the definition of a “service” and include process informationand/or package information (described above with respect to adescription of a managed server 130 within the administrative domainstate 320).

For example, consider a function-level instruction that allows access toonly the Apache service inbound on port 80 (i.e., where the managedserver 130 is the “provider” or endpoint). The managed server 130expresses this function-level instruction in the management moduleconfiguration 134 to allow access on port 80 only after evaluating theassociated condition, which concerns whether the application (executingon that server) that is listening on port 80 is actually Apache and notsome other application (rogue or otherwise). The managed server 130expresses this function-level instruction in the management moduleconfiguration 134 only after determining that the associated conditionevaluates to “true.” If the associated condition evaluates to “false,”then the managed server 130 does not express this function-levelinstruction in the management module configuration 134. As a result, thenetwork traffic is blocked.

In one embodiment, a managed server 130 monitors its outboundconnections. The managed server 130 compares outbound network traffic toits internal process table to determine which processes in that tableare establishing those outbound connections. The managed server 130 canenforce a rule that allows only certain processes (given a set ofrequirements, mentioned above) to establish an outbound connection.

In one embodiment (not shown), the policy compilation module 410 islocated at the global manager 120 instead of at the managed server 130.In that embodiment, the global manager 120 does not send managementinstructions to the managed server 130. Instead, the managed server 130sends its local state to the global manager 120. After the policycompilation module 410 generates the management module configuration 134(at the global manager 120), the management module configuration 134 issent from the global manager 120 to the managed server 130.

The local state update (LSU) module 420 monitors the local state of themanaged server 130 and sends local state information to the globalmanager 120. In one embodiment, the LSU module 420 determines an initiallocal state of the managed server 130, stores appropriate local stateinformation in the local state repository 400, and sends that localstate information to the global manager 120. The LSU module 420determines the local state of the managed server 130 by inspectingvarious parts of the server's operating system (OS) and/or file system.For example, the LSU module 420 obtains service information from the OS'kernel tables (networking information), the OS' system tables (packageinformation), and the file system (files and hash values). The LSUmodule 420 obtains network exposure information from the OS' kernel andand/or OS-level data structures.

After the LSU module 420 sends the initial local state information tothe global manager 120, the LSU module monitors changes to the localstate. The LSU module monitors changes by, for example, polling (e.g.,performing inspections periodically) or listening (e.g., subscribing toan event stream). The LSU module 420 compares recently-obtained localstate information to information already stored in the local staterepository 400. If the information matches, then the LSU module 420takes no further action (until local state information is obtainedagain). If they differ, then the LSU module 420 stores therecently-obtained information in the local state repository 400,executes the policy compilation module 410 to re-generate the managementmodule configuration 134 (and re-configures the management module 132accordingly), and notifies the global manager 120 of the change. In oneembodiment, the LSU module 420 sends changes to local state informationto the global manager 120 in “diff” format. For example, the diff formatspecifies a type of local state information (e.g., operating system) anda new value for that information type. In another embodiment, the LSUmodule 420 sends the entire contents of the local state repository 400to the global manager 120.

FIG. 5 is a flowchart illustrating a method 500 of generating managementinstructions for a particular managed server 130, according to oneembodiment. Other embodiments can perform the steps in different ordersand can include different and/or additional steps. In addition, some orall of the steps can be performed by entities other than those shown inFIG. 1. In one embodiment, the method 500 is executed multiple times(e.g., once for each managed server 130 in an administrative domain150).

When the method 500 starts, the state of the administrative domain'scomputer network infrastructure 320 and an administrative domain-widemanagement policy 330 have already been stored in the repository 300 ofthe global manager 120. At this point, the method 500 begins.

In step 510, the administrative domain state 320 and the administrativedomain-wide management policy 330 are accessed. For example, the policyengine module 340 sends a request to the repository 300 and receives theadministrative domain state 320 and the administrative domain-widemanagement policy 330 in response.

In step 520, one or more relevant rules are determined. For example, thepolicy engine module 340 executes the relevant rules module 350,providing as input the administrative domain-wide management policy 330and the UID of the particular managed server 130. The relevant rulesmodule 350 outputs a set of rules that are relevant to that server(management policy perspective).

In step 530, actors are enumerated. For example, the policy enginemodule 340 executes the actor enumeration module 370, providing as inputthe administrative domain state 320. The actor enumeration module 370generates a representation of the managed servers 130 and unmanageddevice groups (UDGs) within the administrative domain state 320 in anenumerated form (actor-sets).

In step 540, one or more function-level instructions are generated. Forexample, the policy engine module 340 executes the function-levelinstruction generation module 360, providing as input the managementpolicy perspective (generated in step 520). The function-levelinstruction generation module 360 generates function-level instructions.

In step 550, one or more relevant actors is determined. For example, thepolicy engine module 340 executes the relevant actors module 380,providing as input the actor-sets (generated in step 530) and themanagement policy perspective (generated in step 520). The relevantactors module 380 outputs only those actor-sets that are relevant tothose rules (relevant actor-sets).

In step 560, management instructions are sent to the particular managedserver 130. For example, the policy engine module 340 sends thefunction-level instructions (generated in step 540) and the relevantactor-sets (generated in step 550) to the particular managed server 130.

Note that steps 520 and 540 concern generating the management policyperspective (and resulting function-level instructions) for a particularmanaged server 130, while steps 530 and 550 concern generating the actorperspective for that managed server. The generation of the managementpolicy perspective and the generation of the actor perspective areminimally dependent on each other, since step 520 generates a set ofrules that is used by step 550. Even so, keeping the management policycalculations (i.e., steps 520 and 540) and the actor-set calculations(i.e., steps 530 and 550) separate enhances the scalability of thepolicy engine module 340. Since the management policy calculations andthe actor-set calculations are kept mostly separate, they can beperformed in parallel (e.g., even for the same managed server 130). Inaddition, perspective calculations for different managed servers 130 canalso be performed in parallel. Also, if an actor changes, then only theactor-sets need to be recalculated. (The function-level instructions donot need to be recalculated.) If a rule changes, then only thefunction-level instructions and the relevant actor-sets need to berecalculated. (The actors do not need to be re-enumerated.)

FIG. 6 is a flowchart illustrating a method 600 of generating aconfiguration 134 for a management module 132 of a managed server 130,according to one embodiment. Other embodiments can perform the steps indifferent orders and can include different and/or additional steps. Inaddition, some or all of the steps can be performed by entities otherthan those shown in FIG. 1.

When the method 600 starts, information regarding the local state of themanaged server 130 has already been stored in the local state repository400 of the policy implementation module 136 in the managed server 130.At this point, the method 600 begins.

In step 610, management instructions are received from the globalmanager 120. For example, the policy compilation module 410 receivesfunction-level instructions and relevant actor-sets from the globalmanager 120.

In step 620, the local state is accessed. For example, the policycompilation module 410 accesses information regarding the local state ofthe managed server 130 that is stored in the local state repository 400.

In step 630, a management module configuration 134 is generated. Forexample, the policy compilation module 410 takes as input the managementinstructions (received in step 610) and the local state (accessed instep 620) and generates a management module configuration 134.

In step 640, a management module 132 is configured. For example, thepolicy compilation module 410 configures the management module 132 tooperate in accordance with the management module configuration 134(generated in step 630).

FIG. 7 is a flowchart illustrating a method 700 of monitoring localstate of a managed server 130 and sending local state information to aglobal manager 120, according to one embodiment. Other embodiments canperform the steps in different orders and can include different and/oradditional steps. In addition, some or all of the steps can be performedby entities other than those shown in FIG. 1.

When the method 700 starts, information regarding local state of themanaged server 130 has already been stored in the local state repository400 of the managed server 130. At this point, the method 700 begins.

In step 710, information regarding the current local state of themanaged server 130 is determined. For example, the LSU module 420determines the local state of the managed server 130 by inspectingvarious parts of the server's operating system (OS) and/or file system.

In step 720, a determination is performed regarding whether informationregarding the current local state differs from information stored in thelocal state repository 400. For example, the LSU module 420 performsthis determination. If the information does not differ, then the methodproceeds to step 730 and ends. If the information does differ, then themethod proceeds to step 740.

In step 740, the differing information is stored in the local staterepository 400. For example, the LSU module 420 performs this step.

In step 750, the management module configuration 134 is re-generated(because the contents of the local state repository 400 have changed)and the management module 132 is re-configured accordingly. For example,the LSU module 420 executes the policy compilation module 410, whichre-generates the management module configuration 134.

In step 760, the differing information is sent to the global manager120. For example, the LSU module 420 performs this step.

FIG. 8 is a flowchart illustrating a method 800 of processing a changeto the state of an administrative domain's computer networkinfrastructure 320, according to one embodiment. Other embodiments canperform the steps in different orders and can include different and/oradditional steps. In addition, some or all of the steps can be performedby entities other than those shown in FIG. 1.

In step 810, a change regarding a particular managed server 130 isreceived. For example, the administrative domain state update (ADSU)module 385 receives an online/offline indicator, an operating systemindicator, network exposure information, and/or service information fromthe managed server 130 as part of local state information.

In step 820, the received information is stored. For example, the ADSUmodule 385 stores the received online/offline indicator, networkexposure information, and/or service information in the administrativedomain state 320 (specifically, in the description of the managed server130 to which the information pertains).

In step 830, the server description is analyzed to determine additionalinformation regarding the server. For example, the ADSU module 385 usesa label/configured characteristic engine to calculate labels/CC valuesfor the server and/or determines whether the server is behind a networkaddress translator (NAT) (and, if it is behind a NAT, what type ofNAT—1:1 or 1:N) and stores that information in the server description.Step 830 is optional.

In step 840, a determination is made regarding whether to update theadministrative domain's actor-sets. For example, the ADSU module 385determines whether to update the administrative domain's actor-setsbased on a change to the managed server's description. If adetermination is made to update the administrative domain's actor-sets,then the method proceeds to step 850. If a determination is made not toupdate the administrative domain's actor-sets, then the method proceedsto step 860.

In step 850, the administrative domain's actor-sets are updated. Forexample, the ADSU module 385 instructs the policy engine module 340 toupdate the administrative domain's actor-sets. In one embodiment (notshown), the ADSU module 385 waits for an event to occur beforeinstructing the policy engine module 340 to update the administrativedomain's actor-sets.

In step 860, a determination is made regarding whether to update themanaged server's management instructions. For example, the ADSU module385 determines whether to update the managed server's managementinstructions based on a change to the managed server's description. If adetermination is made to update the managed server's managementinstructions, then the method proceeds to step 870. If a determinationis made not to update the administrative domain's actor-sets, then themethod proceeds to step 880.

In step 870, the managed server's management instructions are updated.For example, the ADSU module 385 instructs the policy engine module 340to update the managed server's management instructions. In oneembodiment (not shown), the ADSU module 385 waits for an event to occurbefore instructing the policy engine module 340 to update the managedserver's management instructions.

In step 880, the method ends.

The above description is included to illustrate the operation of certainembodiments and is not meant to limit the scope of the invention. Thescope of the invention is to be limited only by the following claims.From the above discussion, many variations will be apparent to oneskilled in the relevant art that would yet be encompassed by the spiritand scope of the invention.

1. A method of processing a change to a state of a particular managedserver within an administrative domain, wherein the administrativedomain includes a plurality of managed servers that use managementinstructions to configure management modules so that the configuredmanagement modules implement an administrative domain-wide managementpolicy that comprises a set of one or more rules, the method comprising:modifying a first description of the particular managed server toindicate the particular managed server's changed state, therebyspecifying a second description of the particular managed server;comparing the unmodified first description to the second description,thereby specifying a description change; determining, based on thedescription change, whether to update management instructions previouslysent to the particular managed server; and responsive to determining toupdate the particular managed server's management instructions:determining, based on the second description, which rules within the setof rules are currently relevant to the particular managed server,thereby specifying currently-relevant rules; determining whether thecurrently-relevant rules differ from previously-relevant rules, whereinthe previously-relevant rules were determined based on the unmodifiedfirst description; and responsive to determining that thecurrently-relevant rules are identical to the previously-relevant rules,taking no further action.
 2. The method of claim 1, further comprisingresponsive to determining to update the particular managed server'smanagement instructions and responsive to determining that thecurrently-relevant rules differ from the previously-relevant rules:determining a rule that should be added, removed, or modified relativeto the previously-relevant rules; generating, based on the determinedrule, a function-level instruction; and sending, to the particularmanaged server, the function-level instruction and an instruction toadd, remove, or modify the function-level instruction.
 3. The method ofclaim 1, further comprising responsive to determining to update theparticular managed server's management instructions and responsive todetermining that the currently-relevant rules differ from thepreviously-relevant rules: updating cached actor-sets to indicate theparticular managed server's changed state, thereby specifying updatedactor-sets; determining which updated actor-sets are relevant to theparticular managed server, thereby specifying currently-relevant updatedactor-sets; determining whether the currently-relevant updatedactor-sets differ from actor-sets previously sent to the particularmanaged server; and responsive to determining that thecurrently-relevant updated actor-sets are identical to thepreviously-sent actor-sets, taking no further action.
 4. The method ofclaim 3, further comprising responsive to determining that thecurrently-relevant updated actor-sets differ from the previously-sentactor-sets: determining an updated actor-set that should be added,removed, or modified relative to the previously-sent actor-sets; andsending, to the particular managed server, the updated actor-set and aninstruction to add, remove, or modify the updated actor-set.
 5. Themethod of claim 1, wherein the description change comprises anoffline/online change, a label set change, a configured characteristicchange, or a network exposure information change.
 6. The method of claim1, wherein determining whether to update management instructionspreviously sent to the particular managed server comprises: determiningwhether the description change indicates that the particular managedserver went from online to offline; and responsive to determining thatthe description change indicates that the particular managed server wentfrom online to offline, determining not to update the particular managedserver's management instructions.
 7. The method of claim 1, whereindetermining whether to update management instructions previously sent tothe particular managed server comprises: determining whether thedescription change indicates that the particular managed server wentfrom offline to online; and responsive to determining that thedescription change indicates that the particular managed server wentfrom offline to online, determining to update the particular managedserver's management instructions.
 8. The method of claim 1, whereindetermining whether to update management instructions previously sent tothe particular managed server comprises: determining whether thedescription change comprises a label set change or a configuredcharacteristic change; and responsive to determining that thedescription change comprises a label set change or a configuredcharacteristic change, determining to update the particular managedserver's management instructions.
 9. The method of claim 1, whereindetermining whether to update management instructions previously sent tothe particular managed server comprises: determining whether thedescription change comprises a network exposure information change; andresponsive to determining that the description change comprises anetwork exposure information change, determining to update theparticular managed server's management instructions.
 10. The method ofclaim 1, further comprising, prior to comparing the unmodified firstdescription to the second description: determining, based on the seconddescription, additional information regarding the particular managedserver; and modifying the second description to indicate the additionalinformation.
 11. A non-transitory computer-readable storage mediumstoring computer program modules for processing a change to a state of aparticular managed server within an administrative domain, wherein theadministrative domain includes a plurality of managed servers that usemanagement instructions to configure management modules so that theconfigured management modules implement an administrative domain-widemanagement policy that comprises a set of one or more rules, thecomputer program modules executable to perform steps comprising:modifying a first description of the particular managed server toindicate the particular managed server's changed state, therebyspecifying a second description of the particular managed server;comparing the unmodified first description to the second description,thereby specifying a description change; determining, based on thedescription change, whether to update management instructions previouslysent to the particular managed server; and responsive to determining toupdate the particular managed server's management instructions:determining, based on the second description, which rules within the setof rules are currently relevant to the particular managed server,thereby specifying currently-relevant rules; determining whether thecurrently-relevant rules differ from previously-relevant rules, whereinthe previously-relevant rules were determined based on the unmodifiedfirst description; and responsive to determining that thecurrently-relevant rules are identical to the previously-relevant rules,taking no further action.
 12. The computer-readable storage medium ofclaim 11, further comprising responsive to determining to update theparticular managed server's management instructions and responsive todetermining that the currently-relevant rules differ from thepreviously-relevant rules: determining a rule that should be added,removed, or modified relative to the previously-relevant rules;generating, based on the determined rule, a function-level instruction;and sending, to the particular managed server, the function-levelinstruction and an instruction to add, remove, or modify thefunction-level instruction.
 13. The computer-readable storage medium ofclaim 11, further comprising responsive to determining to update theparticular managed server's management instructions and responsive todetermining that the currently-relevant rules differ from thepreviously-relevant rules: updating cached actor-sets to indicate theparticular managed server's changed state, thereby specifying updatedactor-sets; determining which updated actor-sets are relevant to theparticular managed server, thereby specifying currently-relevant updatedactor-sets; determining whether the currently-relevant updatedactor-sets differ from actor-sets previously sent to the particularmanaged server; and responsive to determining that thecurrently-relevant updated actor-sets are identical to thepreviously-sent actor-sets, taking no further action.
 14. Thecomputer-readable storage medium of claim 13, further comprisingresponsive to determining that the currently-relevant updated actor-setsdiffer from the previously-sent actor-sets: determining an updatedactor-set that should be added, removed, or modified relative to thepreviously-sent actor-sets; and sending, to the particular managedserver, the updated actor-set and an instruction to add, remove, ormodify the updated actor-set.
 15. The computer-readable storage mediumof claim 11, wherein the description change comprises an offline/onlinechange, a label set change, a configured characteristic change, or anetwork exposure information change.
 16. The computer-readable storagemedium of claim 11, wherein determining whether to update managementinstructions previously sent to the particular managed server comprises:determining whether the description change indicates that the particularmanaged server went from online to offline; and responsive todetermining that the description change indicates that the particularmanaged server went from online to offline, determining not to updatethe particular managed server's management instructions.
 17. Thecomputer-readable storage medium of claim 11, wherein determiningwhether to update management instructions previously sent to theparticular managed server comprises: determining whether the descriptionchange indicates that the particular managed server went from offline toonline; and responsive to determining that the description changeindicates that the particular managed server went from offline toonline, determining to update the particular managed server's managementinstructions.
 18. The computer-readable storage medium of claim 11,wherein determining whether to update management instructions previouslysent to the particular managed server comprises: determining whether thedescription change comprises a label set change or a configuredcharacteristic change; and responsive to determining that thedescription change comprises a label set change or a configuredcharacteristic change, determining to update the particular managedserver's management instructions.
 19. The computer-readable storagemedium of claim 11, wherein determining whether to update managementinstructions previously sent to the particular managed server comprises:determining whether the description change comprises a network exposureinformation change; and responsive to determining that the descriptionchange comprises a network exposure information change, determining toupdate the particular managed server's management instructions.
 20. Asystem for processing a change to a state of a particular managed serverwithin an administrative domain, wherein the administrative domainincludes a plurality of managed servers that use management instructionsto configure management modules so that the configured managementmodules implement an administrative domain-wide management policy thatcomprises a set of one or more rules, the system comprising: anon-transitory computer-readable storage medium storing computer programmodules executable to perform steps comprising: modifying a firstdescription of the particular managed server to indicate the particularmanaged server's changed state, thereby specifying a second descriptionof the particular managed server; comparing the unmodified firstdescription to the second description, thereby specifying a descriptionchange; determining, based on the description change, whether to updatemanagement instructions previously sent to the particular managedserver; and responsive to determining to update the particular managedserver's management instructions: determining, based on the seconddescription, which rules within the set of rules are currently relevantto the particular managed server, thereby specifying currently-relevantrules; determining whether the currently-relevant rules differ frompreviously-relevant rules, wherein the previously-relevant rules weredetermined based on the unmodified first description; and responsive todetermining that the currently-relevant rules are identical to thepreviously-relevant rules, taking no further action; and a computerprocessor for executing the computer program modules.